Printed circuit boards (PCBs) are widely used in the electronics industry for assembling electronic assemblies. PCBs may be manufactured from stacks of dielectric sheets, sometimes called “prepreg,” some or all of which may have a conductive film on one or both surfaces. Some of the conductive films may be patterned, using lithographic techniques, to form conducting traces that are used to make interconnections within circuits that may contain a variety of circuit elements, e.g., resistors, capacitors, inductors, transistors, fuses, integrated circuits (ICs), trim pots, electro-acoustic devices, microelectromechanicanical devices (MEMs), electro-optical devices, microprocessing chips, memory chips, multi-pin connectors, and various types of sensors, etc. Others of the conductive films may be left substantially intact and may act as ground or power “planes.” These dielectric sheets may be formed into an integral “board” structure such as by pressing the stacked up sheets under pressure.
To make electrical connections to the traces or ground/power planes holes may be drilled through the board. These holes, or “vias,” are filled or plated with metal such that a via will be electrically connected to any of the interior conductive traces or planes through which it passes.
To attach components to the PCB, “tails” from the components may be inserted into the vias, with or without using solder. Alternatively, solder pads may be formed on a surface of the board connecting to a via, and a tail of a component may be soldered to such a pad. As a result, electrical traces and vias may be formed within a PCB.